1. Field of the Invention
The present invention relates generally to computer-assisted design of vehicles and, more specifically, to a system and method of interactive evaluation of a geometric model in the computer-assisted design of a vehicle.
2. Description of the Related Art
Vehicle design, and in particular the design of an automotive vehicle, has advanced to a state in which computer assisted design techniques are frequently incorporated in the development of a new vehicle, or redesign of an existing vehicle. Enhanced visualization software tools allow for interactive display and manipulation of large geometric models, including models developed using computer aided design (CAD). In the field of vehicle design, the use of computer aided design and visualization techniques are especially beneficial in designing, packaging, and assembling the various systems incorporated within the vehicle, to maximize the design and functional capabilities of these vehicles. Advantageously, potential vehicle system designs can be considered in a timely and cost-effective manner by analyzing a digital representation of a proposed design, versus preparing an actual vehicle model.
One aspect of the design task for a vehicle is the coexistence of a CAD generated geometric model and a physical model. An advantage of the physical model is that it provides a physical representation of the design that can be evaluated visually and by touch. For example, a clay model allows a designer to assess a surface quality of the model through multi-fingered, two handed, dexterous manipulation of the model. Designers often trace the contour of a vehicle surface with their fingertips and palm, to obtain tactile information to assess surface fairness. A disadvantage of the physical model relates to transforming the physical model back into the original CAD format after the designer has modified the physical model.
The geometric model of a proposed design is constructed using a technique such as computer-aided design (CAD). An advantage of a CAD model is that known mathematical tools, such as computer-aided engineering (CAE), are available to constrain and guide the designer in evaluating the design. Also, the construction steps involved in creating the geometric model can be recorded for later use. The geometric model can easily be updated using the construction steps in light of a new set of parameters. A disadvantage of a CAD model relates to viewing a 3-dimensional model in 2-dimensions on a display device.
Recently, designers have utilized virtual reality simulation techniques to provide a bridge between the physical model and the CAD model. Virtual reality allows a user to interact with a virtual environment, including a virtual object in the virtual environment, as if the user was actually immersed in the virtual environment. It should be appreciated that a virtual object within the virtual environment may include a virtual surface.
A user-friendly physical device, such as a haptic device, serves as an interface between the user and the virtual environment. Advantageously, the haptic device reproduces at a high rate of speed the sensation of freely moving an object within a constrained environment by determining the forces exchanged between the interacting geometries. This process is frequently referred to as haptic rendering. An example of a haptic interface is disclosed in U.S. Pat. No. 5,694,013 to Stewart et al., entitled “Force Feedback Haptic Interface for a Three-Dimensional CAD Surface”, the disclosure of which is incorporated by reference.
Haptic rendering provides the user with information regarding the virtual surface using force feedback from a single point of contact. In particular, haptic browsing refers to the tactile interaction and visualization of the geometric surface using a haptic interface. An example of a methodology of haptic browsing is disclosed in U.S. Pat. No. 5,844,392 to Peurach et al., entitled “Haptic Browsing”, the disclosure of which is incorporated by reference. While the method disclosed by Peurach et al. '392 uses haptics to present information regarding a single point, it does not constrain the haptic interface to the surface of the geometric model to convey kinesthetic or tactile information. Thus, there is a need in the art for a system and method of interactive evaluation of a geometric model using a haptic interface constrained to a virtual surface within the virtual environment, in order to assess a geometric property associated with the virtual surface.